Libc-498.tar.gz

[apple/libc.git] / stdlib / div-fbsd.c

diff --git a/stdlib/div-fbsd.c b/stdlib/div-fbsd.c
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+/*
+ * Copyright (c) 1990, 1993
+ *     The Regents of the University of California.  All rights reserved.
+ *
+ * This code is derived from software contributed to Berkeley by
+ * Chris Torek.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. All advertising materials mentioning features or use of this software
+ *    must display the following acknowledgement:
+ *     This product includes software developed by the University of
+ *     California, Berkeley and its contributors.
+ * 4. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#if defined(LIBC_SCCS) && !defined(lint)
+static char sccsid[] = "@(#)div.c      8.1 (Berkeley) 6/4/93";
+#endif /* LIBC_SCCS and not lint */
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD: src/lib/libc/stdlib/div.c,v 1.2 2002/03/22 21:53:10 obrien Exp $");
+
+#include <stdlib.h>            /* div_t */
+
+div_t
+div(num, denom)
+       int num, denom;
+{
+       div_t r;
+
+       r.quot = num / denom;
+       r.rem = num % denom;
+       /*
+        * The ANSI standard says that |r.quot| <= |n/d|, where
+        * n/d is to be computed in infinite precision.  In other
+        * words, we should always truncate the quotient towards
+        * 0, never -infinity.
+        *
+        * Machine division and remainer may work either way when
+        * one or both of n or d is negative.  If only one is
+        * negative and r.quot has been truncated towards -inf,
+        * r.rem will have the same sign as denom and the opposite
+        * sign of num; if both are negative and r.quot has been
+        * truncated towards -inf, r.rem will be positive (will
+        * have the opposite sign of num).  These are considered
+        * `wrong'.
+        *
+        * If both are num and denom are positive, r will always
+        * be positive.
+        *
+        * This all boils down to:
+        *      if num >= 0, but r.rem < 0, we got the wrong answer.
+        * In that case, to get the right answer, add 1 to r.quot and
+        * subtract denom from r.rem.
+        */
+       if (num >= 0 && r.rem < 0) {
+               r.quot++;
+               r.rem -= denom;
+       }
+       return (r);
+}